1. Field of the Invention
The present invention relates to a light emitting diode, and particularly relates to a light emitting diode with a structure suitable for a light source for illumination.
2. Description of the Related Art
In recent years, light emitting diodes (LEDs hereafter), being semiconductor light emitting elements, realize high electric and optical conversion efficiency owing to an improvement of a crystal quality. Further, GaN-based and AlGaInP-based high quality crystal can be grown by MOVPE (Metal-Organic Vapor Phase Epitaxy), and therefore high luminance LEDs of blue, green, orange, yellow, and red colors can be manufactured (for example, see patent document 1). Thus, owing to an improvement of the crystal quality, emission efficiency of LEDs are increased and an influence of heat generation is reduced, and use of the light emitting diode in a large current is realized. Therefore, there is a wider application of the light emitting diode to a light source for illumination which requires a high luminance compared with LED for display.
In order to realize a higher output of a light emitting element, a larger-sized element is required and a resistance to a larger power is required. As an effective structure for such higher output and higher efficiency of LED, a flip chip structure using bumps is known (for example, see patent documents 1 and 2). In the flip chip structure, LED chips are used, wherein as shown in FIG. 10, a prescribed semiconductor layer 211 having a light emitting part is grown on a transparent substrate 210 by lamination, with two electrodes 212, 213 formed on the semiconductor layer 211 for current injection, and bumps 214 are formed on the electrodes 212 and 213 respectively. The LED chips with such a flip chip structure are mounted on a metal wiring 215 on the substrate 216 via the bumps 214. In the LED with the flip chip structure, the transparent substrate 210 side is used as a light extraction surface, and a light from the light emitting part is not shielded by electrodes. Therefore, high light extraction efficiency can be realized. Therefore, high light extraction efficiency can be realized.
[Patent Document 1]
    Japanese Patent Laid Open Publication No. 2007-305851[Patent Document 2]    Japanese Patent Laid Open Publication No. 2008-78225
In a structure disclosed in patent document 1, although reliable mounting by wire bonding is enabled, wire bonding needs to be applied to a light emitting element one by one. Therefore, such a structure is unsuitable for mounting a plurality of light emitting elements. Further, there is a problem that light emitted from a semiconductor light emitting part is shielded by bonding wire.
In a flip chip mounting using bumps as disclosed in patent document 2, a plurality of bumps need to be formed for mounting one LED, and therefore there is a problem that it is not easy to control quantity and height of each bump and not easy to perform positioning and bonding for LED mounting, thus easily generating a bonding failure, and making it difficult to improve productivity and yield rate.